REGIONAL PROPAGATION MEDIUM PARAMETERS FOR GROUND MOTION ESTIMATION

doi:10.3969/j.issn.0253-4967.2024.05.006

Abstract

Abstract:

Estimating the possible ground motion generated by future earthquakes can provide input for seismic design, which is an important research direction in engineering seismology. It is widely used in seismic risk analysis, earthquake zoning, post-earthquake emergency, earthquake disaster mitigation planning. Ground motion is estimated in two ways: first, the attenuation relation of ground motion is simplified to express the relationship between ground motion and earthquake size, focal characteristics, propagation medium and site influence; Second, the near-fault ground motion of large earthquakes is synthesized by using finite fault source model and Green’s function. Both of the two ways describe the influence of source, propagation medium and site conditions. Among them, the propagation of seismic waves in the medium can be expressed in terms of geometric spreading term and inelastic attenuation term. In this study, the characteristics of these two regional propagation media are studied from two perspectives: the geometrical spreading term and the inelastic attenuation term. Firstly, the northeastern region of Japan, with abundant seismic records, is taken as the research area, and the effects of magnitude, focal depth, and Moho depth are discussed by using a genetic algorithm. The results show that the Moho depth significantly influences the geometrical spreading parameters. The results were applied to the regions of Sichuan, Xinjiang and Yunnan in western China, and the geometric spreading terms were determined according to the depth of the Moho plane and the least square method was used to fit the geometric spreading term. On this basis, from the geological point of view, according to the geological time, earth heat flow value, surface elevation, Moho buried depth, upper crust shear wave velocity and seismic activity, the regions are re-divided, and the inelastic attenuation parameters Q₀ and η are obtained by using genetic algorithm. According to the above six factors, it can be found that the stress drop is distributed in 30-130bar, κ₀ in 0.025-0.06s, Q₀ in 220-350, η in 0.56-0.96. Among them, the discussion of the influence of various influencing factors on the Q₀ in this paper can be described as follows: When grouped according to geological time, the value of Q₀ decreases from Paleozoic to Cenozoic. When divided into two groups according to geothermal conditions, the Q₀ value of the low heat area is greater than that of the high heat area. When it is divided into three groups according to the elevation, which are less than 1 000m, between 1 000 and 3 000m and above 3 000m, the Q₀ value decreases with the elevation increase. When the buried depth of the Moho surface is divided into deep and shallow buried areas, the Q₀ value of the deep buried area is greater than that of the shallow buried area. When the shear wave velocity of the upper crust is divided into two groups, the Q₀ value of the low-speed region is smaller than that of the high-speed region. When the seismic activity is divided into strong seismic activity and weak seismic activity, the Q₀ value of the weak seismic activity region is greater than that of the strong seismic activity region. By analyzing the inversion results, some rules of quality factor distribution in the study area can be summarized: seismic wave attenuation is faster and Q value is usually lower in the areas with high ground heat flow, shallow Moho surface, low shear wave velocity and strong seismic activity; With the increase of geological time from ancient to present and elevation, the Q value decreases gradually. Combined with the calculated value of the regional crustal medium parameter Q, which is required for ground motion estimation, the division scheme of the inversion area is given, that is, the eastern part of Sichuan and Tianshan region of Xinjiang are the regions with high Q values, Yunnan, central and western parts of Sichuan and Kashi region of Xinjiang are the regions with low Q values, and the northwestern part of Yunnan and west and central part of Sichuan are the regions with relatively lower Q values. During the study of the inelastic attenuation term, the study area was redivided according to the influence of a single factor. In the follow-up research, the study area will be redivided according to the cross-over of different influencing factors to explore the influence of the inelastic attenuation term. At the same time, the next step will continue to improve the zoning standards in western China and draw the zoning map.

Key words: Ground motion estimation, Geometric spreading, Inelastic attenuation, Quality factor

摘要：

地震动估计是抗震设计和风险评估的重要输入来源。地震动估计中, 地震波在地壳介质中的传播可用几何扩散项和非弹性衰减项表达。文中针对这2项区域传播介质特性, 从几何扩散项和非弹性衰减项2个角度分别开展研究。首先, 以地震记录丰富的日本东北部地区为研究区, 使用遗传算法反演几何扩散项参数并讨论震级、震源深度及莫霍面深度的影响。结果表明: 莫霍面埋深对几何扩散项参数的影响最大。将此结果用于中国西部的四川、新疆和云南地区, 按照莫霍面深度分区并分段拟合几何扩散项参数。在此基础上, 从地质学的角度重新划分区域, 借助遗传算法反演得到不同分区的非弹性衰减项参数Q₀和η等。结果表明: 在大地热流数值较高、莫霍面较浅、上地壳剪切波速较低、地震活动较强烈的地区, 地震波衰减较快, 通常Q值较低; 在地质年代由古及今、高程增加的情况下, Q值逐渐减小。面向地震动估计所需的区域地壳介质参数Q值, 给出了反演区域范围的划分方案, 即四川的东部地区和新疆天山地区为高Q值区域, 云南、四川中西部地区和新疆喀什地区为低Q值区域。其中, 云南西北部和四川中西部为Q值相对更低的地区。

关键词: 地震动估计, 几何扩散项, 非弹性衰减项, 品质因子

ZHENG Xing-qun, TAO Zheng-ru, BAI Kai. REGIONAL PROPAGATION MEDIUM PARAMETERS FOR GROUND MOTION ESTIMATION[J]. SEISMOLOGY AND GEOLOGY, 2024, 46(5): 1091-1105.

郑兴群, 陶正如, 白凯. 面向地震动估计需求的区域传播介质参数[J]. 地震地质, 2024, 46(5): 1091-1105.

Figures/Tables 14

Fig. 1 Distribution of stations and epicenters in northeastern Japan.

Fig. 2 Distribution of stations and epicenters in study area.

Table 1 Inversion range of regional parameters in northeastern Japan

反演参数	取值范围
R₁/km	20~80
R₂/km	80~150
b₁	0.8~1.5
b₂	-0.3~0.7
b₃	0.49~0.51
Q₀	90~300
η	0.6~1.0

Table 2 Parameter inversion results of each magnitude subsets

M_W	R₁/km	R₂/km	b₁	b₂	b₃	Q₀	η
3.5~4.5	32	100	1.43	-0.05	0.50	168	0.80
4.5~5.5	30	148	1.40	0.10	0.50	167	0.79
5.5~6.5	29	147	1.34	0.20	0.50	165	0.81
≥6.5	30	148	1.10	0.28	0.50	170	0.77

Table 3 Parameter inversion results of focal depth subsets

H/km	R₁/km	R₂/km	b₁	b₂	b₃	Q₀	η
0~8	27	147	1.44	-0.18	0.50	178	0.81
8~16	29	145	1.42	0.14	0.50	170	0.81
16~30	25	148	1.36	0.21	0.50	182	0.85

Table 4 Parameter inversion results of Moho depth subsets

D/km	R₁/km	R₂/km	b₁	b₂	b₃	Q₀	η
≤25	25	82	1.03	0.08	0.50	168	0.74
25~29	30	95	1.40	0.02	0.50	173	0.78
≥29	35	100	1.38	0.11	0.50	170	0.75

Table 5 Fitting results

莫霍面埋深/km	频率/Hz	R₁/km	R₂/km
25~35	1	45	104
25~35	2	45	104
25~35	4	45	109
25~35	8	45	109
35~45	1	64	119.5
35~45	2	64	119.5
35~45	4	64	119.5
35~45	8	64	119.5
45~60	1	79	139
45~60	2	79	139
45~60	4	79	139
45~60	8	71	139

Table 6 Inversion range of parameters in western China

$Δ σ$ /bar	κ₀/s	Q₀	η
1~220	0.01~0.08	90~500	0.2~1.1

Table 6 Inversion range of parameters in western China

$Δ σ$ /bar	κ₀/s	Q₀	η
1~220	0.01~0.08	90~500	0.2~1.1

Table 7 Regional parameters in areas divided by geological age

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
古生代区	87.295	0.0506	340.08	0.801
中生代区	98.386	0.0572	321.41	0.580
新生代区	82.590	0.0555	283.37	0.958

Table 7 Regional parameters in areas divided by geological age

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
古生代区	87.295	0.0506	340.08	0.801
中生代区	98.386	0.0572	321.41	0.580
新生代区	82.590	0.0555	283.37	0.958

Table 8 Regional parameters in areas divided by terrestrial heat flow

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
低热区	52.172	0.0395	381.33	0.735
高热区	104.096	0.0304	220.58	0.852

Table 8 Regional parameters in areas divided by terrestrial heat flow

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
低热区	52.172	0.0395	381.33	0.735
高热区	104.096	0.0304	220.58	0.852

Table 9 Regional parameters in areas divided by elevation

区域高程	$Δ σ$ /bar	κ₀/s	Q₀	η
<1000m	88.567	0.0399	362.68	0.601
1000~3000m	128.183	0.0522	335.59	0.654
>3000m	69.119	0.0517	281.47	0.715

Table 9 Regional parameters in areas divided by elevation

区域高程	$Δ σ$ /bar	κ₀/s	Q₀	η
<1000m	88.567	0.0399	362.68	0.601
1000~3000m	128.183	0.0522	335.59	0.654
>3000m	69.119	0.0517	281.47	0.715

Table10 Regional parameters in areas divided by depth of Moho surface

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
浅埋深区	81.507	0.0242	222.10	0.671
深埋深区	110.338	0.0346	301.64	0.591

Table10 Regional parameters in areas divided by depth of Moho surface

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
浅埋深区	81.507	0.0242	222.10	0.671
深埋深区	110.338	0.0346	301.64	0.591

Table11 Regional parameters in areas divided by shear wave velocity in the upper crust

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
低速区	30.866	0.0379	227.16	0.882
高速区	80.874	0.0459	344.92	0.620

Table11 Regional parameters in areas divided by shear wave velocity in the upper crust

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
低速区	30.866	0.0379	227.16	0.882
高速区	80.874	0.0459	344.92	0.620

Table12 Regional parameters in areas divided by seismic activity

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
弱活动区	34.027	0.0425	291.43	0.751
强活动区	82.740	0.0526	237.80	0.555

Table12 Regional parameters in areas divided by seismic activity

分区	$Δ σ$ /bar	κ₀/s	Q₀	η
弱活动区	34.027	0.0425	291.43	0.751
强活动区	82.740	0.0526	237.80	0.555

References 48

[1]	阿衣仙姑·买买提, 尼鲁帕尔·买买吐孙, 祖丽皮亚·巴克, 等. 2015. 南天山西段及交会区介质品质因子Q值特征研究[J]. 高原地震, 27(1): 23—30.
	AYIXIANGU·Maimaiti, NILUPAER·Maimaitusun, ZULIPIYA·Baker, et al. 2015. Research on quality factor Q of small and moderate earthquakes in the western part of southern Tianshan[J]. Plateau Earthquake Research, 27(1): 23—30 (in Chinese).
[2]	白凯. 2020. 几何衰减项影响因素的分析[D]. 哈尔滨: 中国地震局工程力学研究所.
	BAI Kai. 2020. Analysis of influencing factors of geometric spreading function[D]. Institute of Engineering Mechanics, China Earthquake Administration, Harbin (in Chinese).
[3]	曹泽林. 2020. 基于FK法的三维宽频带强地震动场的合成[D]. 哈尔滨: 哈尔滨工业大学.
	CAO Ze-lin. 2020. Synthesis of 3D wide band strong ground motion field based on FK method[D]. Harbin Institute of Technology, Harbin (in Chinese).
[4]	曹泽林, 陶夏新, 陶正如, 等. 2022. FK法合成地震动的频带范围研究[J]. 地震学报, 44(1): 145—157.
	CAO Ze-lin, TAO Xia-xin, TAO Zheng-ru, et al. 2022. Research on bandwidth of ground motion simulated using FK approach[J]. Acta Seismologica Sinica, 44(1): 145—157 (in Chinese).
[5]	啜永清, 苏燕, 贾建喜, 等. 2004. 山西地区非弹性衰减系数, 场地响应和几种震源参数的研究[J]. 地震学报, 26(4): 369—378.
	CHUO Yong-qing, SU Yan, JIA Jian-xi, et al. 2004. Study on inelastic attenuation coefficient, site response and source parameters in Shanxi region[J]. Acta Seismologica Sinica, 26(4): 369—378 (in Chinese).
[6]	崔安平. 2013. 用地震观测台网的小震记录建立川滇强地震动衰减关系[D]. 哈尔滨: 中国地震局工程力学研究所.
	CUI An-ping. 2013. The attenuation relationship of Sichuan and Yunnan strong ground motion is established by using the small earthquake records of the seismic observation network[D]. Institute of Engineering Mechanics, China Earthquake Administration, Harbin (in Chinese).
[7]	傅磊, 李小军, 荣棉水, 等. 2018. 基于强震动数据的龙门山地区地震动预测模型参数反演[J]. 地震学报, 40(3): 374—386.
	FU Lei, LI Xiao-jun, RONG Mian-shui, et al. 2018. Parameter estimation of ground-motion prediction model in Longmenshan region based on strong motion data[J]. Acta Seismologica Sinica, 40(3): 374—386 (in Chinese).
[8]	高长起. 1994. 地质年代的单位划分及其名称溯源[J]. 生物学通报, 29(7): 25.
	GAO Chang-qi. 1994. Unit division of geological time and its name tracing[J]. Biological Bulletin, 29(7): 25 (in Chinese).
[9]	郝美仙, 尹战军, 张帆. 2017. 利用数字化波形研究内蒙古东部地区非弹性衰减系数、场地响应和震源参数[J]. 山西地震, 170(2): 42—46.
	HAO Mei-xian, YIN Zhan-jun, ZHANG Fan. 2017. Study on the inelastic attenuation coefficient, site response and source parameters in eastern Inner Mongolia by digital waveform[J]. Earthquake Research in Shanxi, 170(2): 42—46.
[10]	胡圣标, 何丽娟, 汪集旸. 2001. 中国大陆地区大地热流数据汇编(第三版)[J]. 地球物理学报, 44(5): 611—626.
	HU Sheng-biao, HE Li-juan, WANG Ji-yang. 2001. Compilation of heat flow data in the China continental area(3^rd edition)[J]. Chinese Journal of Geophysic, 44(5): 611—626 (in Chinese).
[11]	胡聿贤. 2006. 地震工程学[M]. 北京: 地震出版社.
	HU Yu-xian. 2006. Earthquake Engineering[M]. Seismological Press, Beijing (in Chinese).
[12]	黄玉龙, 郑斯华, 刘杰, 等. 2003. 广东地区地震动衰减和场地响应的研究[J]. 地球物理学报, 46(1): 54—61.
	HUANG Yu-long, ZHENG Si-hua, LIU Jie, et al. 2003. Attenuation of ground motion and site response in Guangdong region[J]. Chinese Journal of Geophysics, 46(1): 54—61 (in Chinese).
[13]	纪林建. 2018. 基于地震学衰减关系研究中的若干问题的讨论[D]. 哈尔滨: 中国地震局工程力学研究所.
	JI Lin-jian. 2018. Some issues on seismology based ground motion attenuation relationship[D]. Institute of Engineering Mechanics, China Earthquake Administration, Harbin (in Chinese).
[14]	姜光政, 高堋, 饶松, 等. 2016. 中国大陆地区大地热流数据汇编(第四版)[J]. 地球物理学报, 59(8): 2892—2910.
	JIANG Guang-zheng, GAO Peng, RAO Song, et al. 2016. Compilation of heat flow data in the continental area of China(4^th edition)[J]. Chinese Journal of Geophysics, 59(8): 2892—2910 (in Chinese).
[15]	李文倩. 2014. 用数字地震台网小震数据建立兰州和华北地区强地震动衰减关系[D]. 哈尔滨: 中国地震局工程力学研究所.
	LI Wen-qian. 2014. Establishment of attenuation relationship between strong ground motion in Lanzhou and North China using small earthquake data of digital seismic network[D]. Institute of Engineering Mechanics, China Earthquake Administration, Harbin (in Chinese).
[16]	刘充. 2005. 基于随机振动理论的地震动衰减[D]. 哈尔滨: 哈尔滨工业大学.
	LIU Chong. 2005. Attenuation of ground motion based on random vibration theory[D]. Harbin Institute of Technology, Harbin (in Chinese).
[17]	刘杰, 郑斯华, 黄玉龙. 2003. 利用遗传算法反演耗能衰减函数、震源参数和场地效应[J]. 地震学报, 25(2): 211—218.
	LIU Jie, ZHENG Si-hua, HUANG Yu-long. 2003. Inversion of energy dissipation attenuation function, source parameter and site effect by genetic algorithm[J]. Acta Seismologica Sinica, 25(2): 211—218 (in Chinese).
[18]	刘丽芳, 苏有锦, 刘杰, 等. 2007. 用Moya方法反演云南数字地震台站场地响应[J]. 地震研究, 30(1): 39—42.
	LIU Li-fang, SU You-jin, LIU Jie, et al. 2007. Site effects at Yunnan regional digital seismic stations inversed by Moya method[J]. Journal of Seismological Research, 30(1): 39—42 (in Chinese).
[19]	刘陶钧. 2009. 加利福尼亚关于区域参数的地震动衰减[D]. 哈尔滨: 哈尔滨工业大学.
	LIU Tao-jun. 2009. Ground motion attenuation in California with respect to regional parameters[D]. Harbin Institute of Technology, Harbin (in Chinese).
[20]	马本亮. 2016. 用地震监测台网记录估计强地震动衰减的试验研究[D]. 哈尔滨: 哈尔滨工业大学.
	MA Ben-liang. 2016. Experimental research on ground motion attenuation with seismograms from seismic monitoring network[D]. Harbin Institute of Technology, Harbin (in Chinese).
[21]	马宏生, 汪素云, 裴顺平, 等. 2007. 川滇及周边地区地壳横波衰减的成像研究[J]. 地球物理学报, 50(2): 465—471.
	MA Hong-sheng, WANG Su-yun, PEI Shun-ping, et al. 2007. Q₀ tomography of S wave attenuation in Sichuan-Yunnan and adjacent regions[J]. Chinese Journal of Geophysics, 50(2): 465—471 (in Chinese).
[22]	乔慧珍, 张永久, 程万正, 等. 2006. 川西北地区介质衰减特征研究[J]. 地震地磁观测与研究, 27(4): 1—7.
	QIAO Hui-zhen, ZHANG Yong-jiu, CHENG Wan-zheng, et al. 2006. The inversion of the inelastic coefficient of the medium in North-West of Sichuan Province[J]. Seismological and Geomagnetic Observation and Research, 27(4): 1—7 (in Chinese).
[23]	王勤彩, 高景春, 郑斯华. 2004. 华北中北部地面运动衰减研究[J]. 防灾减灾工程学报, 24(3): 313—319.
	WANG Qin-cai, GAO Jing-chun, ZHENG Si-hua. 2004. Attenuation of ground motion in central and north area of north China[J]. Journal of Disaster Prevention and Mitigation Engineering, 24(3): 313—319 (in Chinese).
[24]	王希伟. 2012. 基于地震学的日本东北地区地震动衰减关系研究[D]. 哈尔滨: 中国地震局工程力学研究所.
	WANG Xi-wei. 2012. Research on attenuation relationship of ground motion in Northeast Japan based on seismology[D]. Institute of Engineering Mechanics, China Earthquake Administration, Harbin (in Chinese).
[25]	赵翠萍, 张智强, 夏爱国, 等. 2004. 利用数字地震波资料研究新疆天山中东段地区的介质衰减特征[J]. 防灾减灾工程学报, 24(3): 300—305.
	ZHAO Cui-ping, ZHANG Zhi-qiang, XIA Ai-guo, et al. 2004. Study of attenuation characteristics of the central and eastern Tianshan, Xinjiang using digital seismic waves[J]. Journal of Disaster Prevention and Mitigation Engineering, 24(3): 300—305 (in Chinese).
[26]	郑浩. 2023. 近地表地层品质因子的频率依赖性研究[J]. 地球物理学进展, 38(1): 419—429.
	ZHENG Hao. 2023. Analysis on frequency dependence of near-surface quality factors[J]. Progress in Geophysics, 38(1): 419—429 (in Chinese).
[27]	Ambraseys N N, Douglas J, Sarma S K, et al. 2005. Equations for the estimation of strong ground motions from shallow crustal earthquakes using data from Europe and the Middle East: Vertical peak ground acceleration and spectral acceleration[J]. Bulletin of Earthquake Engineering, 3(1): 1—53.
[28]	Atkinson G M. 2004. Empirical attenuation of ground-motion spectral amplitudes in southeastern Canada and the northeastern United States[J]. Bulletin of the Seismological Society of America, 94(3): 1079—1095.
[29]	Atkinson G M, Mereu R F. 1992. The shape of ground motion attenuation curves in southeastern Canada[J]. Bulletin of the Seismological Society of America, 82(5): 2014—2031.
[30]	Boore D M. 1983. Stochastic simulation of high-frequency ground motions based on seismological models of the radiated spectra[J]. Bulletin of the Seismological Society of America, 73(6): 1865—1894.
[31]	Boore D M. 2003. Simulation of ground motion using the stochastic method[J]. Pure and Applied Geophysics, 160(3): 635—676.
[32]	Boore D M, Watson-Lamprey J, Abrahamson N A. 2006. Orientation-independent measures of ground motion[J]. Bulletin of the seismological Society of America, 96(4A): 1502—1511.
[33]	Brune J N. 1970. Tectonic stress and the spectra of seismic shear waves from earthquakes[J]. Journal of Geophysical Research, 75(26): 4997—5009.
[34]	Cotton F, Pousse G, Bonilla F, et al. 2008. On the discrepancy of recent European ground-motion observations and predictions from empirical models: Analysis of KiK-net accelerometric data and point-sources stochastic simulations[J]. Bulletin of the Seismological Society of America, 98(5): 2244—2261.
[35]	Hartzell S H. 1978. Earthquake aftershocks as Green’s functions[J]. Geophysical Research Letters, 5(1): 1—4.
[36]	Hartzell S H, Guatteri M, Mai M P, et al. 2005. Calculation of broadband time histories of ground motion, part Ⅱ: Kinematic and dynamic modeling using theoretical Green’s Functions and comparison with the 1994 Northridge earthquake[J]. Bulletin of the Seismological Society of America, 95(2): 614—645.
[37]	Hasegawa H S. 1983. Lg spectra of local earthquakes recorded by the eastern Canada telemetered network and spectral scaling[J]. Bulletin of the Seismological Society of America, 73(4): 1041—1061.
[38]	Hasegawa H S. 1985. Attenuation of Lg waves in the Canada Shield[J]. Bulletin of the Seismological Society of America, 75(6): 1569—1582.
[39]	Husid R. 1967. Gravity effects on the earthquake response of yielding structures[D]. California Institute of Technology, Pasadena, California.
[40]	Mccann M W J, Shah H C. 1979. Determining strong motion duration of earthquake[J]. Bulletin of the Seismological Society of America, 69(4): 1253—1265.
[41]	McGuire R K, Hanks T C. 1980. RMS accelerations and spectral amplitudes of strong ground motion during the San Fernando, California, earthquake[J]. Bulletin of the Seismological Society of America, 70(5): 1907—1919.
[42]	Mitchell B J, Leite L W B, Yu Y K, et al. 1976. Attenuation of Love and Rayleigh waves across the Pacific at periods between 15 and 110 seconds[J]. Bulletin of the Seismological Society of America, 66(4): 1189—1202.
[43]	Morozov I B. 2009. Thirty years of confusion around “scattering” Q[J]. Seismological Research Letters, 80(1): 5—7.
[44]	Ou G B, Herrmann R B. 1990. A statistical model for peak ground motion from local to regional distances[J]. Bulletin of the Seismological Society of America, 80(6A): 1397—1417.
[45]	Rainner T. 1989. Comparison of seven methods for the computation of Q[J]. Physics of the Earth and Planetary Interiors, 55(3-4): 259—268.
[46]	Shen W S, Ritzwoller M H, Kang D, et al. 2016. A seismic reference model for the crust and uppermost mantle beneath China from surface wave dispersion[J]. Geophysical Journal International, 206(2): 956—979.
[47]	Slejko D, Bragato P L. 2005. Empirical ground-motion attenuation relations for the eastern alps in the magnitude range 2.5-6.3[J]. Bulletin of the Seismological Society of America, 95(1): 252—276.
[48]	Street R L, Herrmann R B, Nuttli O W. 1975. Spectral characteristics of the Lg wave generated by central United States earthquakes[J]. Geophysical Journal International, 41(1): 51—63.